U.S. patent application number 10/276104 was filed with the patent office on 2003-10-09 for method and device for generating euv radiation.
Invention is credited to Chichkov, Boris, Egbert, Andr?eacute.
Application Number | 20030189176 10/276104 |
Document ID | / |
Family ID | 7677949 |
Filed Date | 2003-10-09 |
United States Patent
Application |
20030189176 |
Kind Code |
A1 |
Chichkov, Boris ; et
al. |
October 9, 2003 |
Method and device for generating euv radiation
Abstract
The invention relates to a method for generating EUV radiation.
Laser pulses are directed onto photoelectric transducer means (10),
which generate pulses of electrically charged particles (6) as a
result of the action of the laser pulses. The electrically charged
particles are accelerated in an electric field and directed onto a
target (4), in such a way that the target generates a plasma, which
emits EUV radiation, as a result of the action of the electrically
charged particles.
Inventors: |
Chichkov, Boris; (Hannover,
DE) ; Egbert, Andr?eacute;; (Haste, DE) |
Correspondence
Address: |
Robert W Becker & Associates
Suite B
707 Highway East
Tijeras
NM
87059-7382
US
|
Family ID: |
7677949 |
Appl. No.: |
10/276104 |
Filed: |
November 12, 2002 |
PCT Filed: |
March 13, 2002 |
PCT NO: |
PCT/EP02/02772 |
Current U.S.
Class: |
250/396ML ;
250/492.3; 250/504R |
Current CPC
Class: |
H05G 2/003 20130101 |
Class at
Publication: |
250/396.0ML ;
250/492.3; 250/504.00R |
International
Class: |
H01J 037/141; G21G
005/00; G01J 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2001 |
DE |
101 13 064.3 |
Claims
1. Method for the generation of UV radiation, especially EUV
radiation, according to which laser pulses are used for the
production of a plasma that emits UV radiation, especially EUV
radiation, characterized in, that the laser pulses are directed
onto photoelectric transducer means that under the effect of the
laser pulses produce pulses of electrically charged particles, and
that the electrically charged particles are accelerated in an
electrical field and are directed upon a target such that under the
effect of the electrically charged particles the target produces a
plasma that emits UV radiation, especially EUV radiation.
2. Method according to claim 1, characterized in that the
electrically charged particles are electrons.
3. Method according to claim 1, characterized in that at least one
photocathode is used as the photoelectric transducer means.
4. Method according to claims 2 and 3, characterized in that for
the acceleration of the electrons an anode is used to which is
applied a high voltage.
5. Method according to claim 4, characterized in that an
essentially annular anode is used.
6. Method according to claim 1, characterized in that the
electrically charged particles are focused upon the target.
7. Method according to claim 6, characterized in that the
electrically charged particles are focused upon the target via at
least one electromagnetic optics mechanism.
8. Method according to claim 1, characterized in that the target is
provided with droplets of a liquid.
9. Method according to claim 8, characterized in that the liquid is
water or xenon.
10. Method according to claim 1, characterized in that the target
is a cluster target.
11. Method according to claim 1, characterized in that the plasma
is produced in a vaccum.
12. Method according to claim 1, characterized in that the laser
pulses have a high repetition rate of at least approximately 1000
Hz.
13. Method according to claim 1, characterized in that the target
is a highly repetitive target.
14. Device for the generation of UV radiation, especially EUV
radiation, with a laser, which produces laser pulses for the
production of a plasma that emits UV radiation, especially EUV
radiation, characterized in, that the laser directs the laser
pulses upon photoelectric transducer means that under the effect of
the laser pulses produces pulses of electrically charged particles,
and that means are provided for the production of an electrical
field that accelerates the electrically charged particles and
directs them upon a target such that under the effect of the
electrically charged particles the target produces a plasma that
emits UV radiation, especially EUV radiation.
15. Device according to claim 14, characterized in that the
electrically charged particles are electrons.
16. Device according to claim 14, characterized in that the photo
electric transducer means is provided with at least one
photocathode (4).
17. Device according to claim 15 and 16, characterized in that the
means for the production of an electrical field is provided with an
anode (8) to which is applied a high voltage.
18. Device according to claim 17, characterized in that the anode
(8) has a ring-shaped or annular configuration.
19. Device according to claim 14, characterized by means for the
focusing of the electrically charged particles upon the target.
20. Device according to claim 19, characterized in that the means
for the focusing of the electrically charged particles are provided
with at least one electromagnetic optics mechanism.
21. Device according to claim 14, characterized in that the target
is provided with droplets (10) of a liquid.
22. Device according to claim 21, characterized in that the liquid
is water or xenon.
23. Device according to claim 14, characterized in that the target
is a cluster target.
24. Device according to claim 14, characterized in that the
production of the plasma is effected in a vacuum.
25. Device according to claim 14, characterized in that the laser
produces laser pulses having a high repetition rate of at least
approximately 1000 Hz.
26. Device according to claim 14, characterized in that the target
is a highly repetitive target.
Description
[0001] The invention relates to a method of the type mentioned in
the preamble of claim 1, and a device of the type mentioned in the
preamble of claim 14, for the generation of UV radiation,
especially EUV radiation.
[0002] During the manufacture of integrated circuits, to a large
extent methods for the optical projections lithography are utilized
in order to form, upon the surface of semiconductor wafers,
patterns that define the integrated circuits. In so doing, the
dimensions of the projected pattern are primarily a function of the
wavelength of the radiation used for the projection, whereby the
shorter the wavelengths of the radiation used, the finer can be the
patterns that are formed.
[0003] In order in contrast to the known methods for the optical
projections lithography to achieve an extensive miniaturization of
semiconductor circuits, it is known, during the lithography, to use
EUV (Extreme Ultra-Violet) radiation having a wavelength from 11 to
14 nm.
[0004] From the publications "EUV Lithography--The Successor to
Optical Lithography?", Intel Technology Journal Q3 '98, and
"Extreme Ultraviolet Lithography", J. Vac. Sci Technol. B 16 (6),
November/December 1998, methods are known for the generation of EUV
radiation according to which laser pulses are used for the
production of a plasma that emits the EUV radiation. With the known
methods, laser pulses having high repetition rates are directed
upon a target that, for example, is comprised of xenon, whereby
during irradiation of the target a plasma results that emits the
EUV radiation. The EUV radiation generated in this manner can then,
for example, be utilized in the EUV lithography during the
manufacture of semiconductor circuits.
[0005] A drawback of the known methods is that the laser pulses
must have a high energy so that a plasma that emits EUV radiation
can be produced in the desired manner. The high power lasers
required during the known methods are therefore complicated and
expensive, so that it is not possible to have an economical mass
production of semiconductor circuits.
[0006] The object of the invention is to provide a method and a
device for the generation of UV radiation, especially EUV
radiation, according to which the generation of UV radiation,
especially EUV radiation, is possible with straightforward means
and hence an economical manner.
[0007] With regard to the method, this object is realized by the
teaching of claim 1, and with regard to the device is realized by
the teaching of claim 14.
[0008] The invention proceeds from the recognition that an
economical use of lasers during a production of a plasma that emits
EUV radiation is possible only if simple and economical lasers are
utilized, whereby, however, the power of such lasers is not
sufficient for the production of the plasma. Proceeding from this
recognition, the basic concept of the invention is that the laser
pulses not be directed directly upon the target, but rather to
first reinforce the energy of the laser pulses such that a plasma
that emits EUV radiation can be produced in the desired manner. To
increase the energy of the laser pulses, the inventive teaching
proposes that the laser pulses be directed upon photoelectric
transducer means, that, under the effect of the laser pulses,
produce pulses of electrically charged particles. These
electrically charged particles can then, in a straightforward
manner, be accelerated in an electrical field to such an extent
that during a subsequent striking or impingement of the particles
onto the target, a sufficient energy is available in order to
produce a plasma that emits EUV radiation.
[0009] The increase of the energy of the particles, in this
connection, is limited only by the intensity of the electrical
field, so that with an appropriate selection of the intensity or
strength of the field, the energy of the particles can be readily
increased to such an extent that during the subsequent impingement
upon the target, a plasma is produced that emits EUV radiation.
[0010] With the appropriate selection of the strength of the
electrical field, it is thus possible to use lasers having a
relatively low power, which are simple and economical, so that the
inventive teaching enables an economical use of lasers during the
generation of EUV radiation.
[0011] The inventive method can be used everywhere that UV
radiation, especially EUV radiation, is required. The inventive
method is particularly well suited for use in the EUV
lithography.
[0012] In principle, any desired electrically charged particles
could be used. Expediently, however, the electrically charged
particles are electrons, whereby pursuant to a further development
the photoelectric transducer means have at least one photocathode
that upon irradiation with laser pulses emits pulses of electrons.
Such photocathodes are economical, so that pursuant to this further
development the inventive method can be carried out particularly
easily and hence economically.
[0013] To increase the energy of the electrons, with the
aforementioned embodiment it is expedient that for the acceleration
of the electrons an anode is used to which is applied a high
voltage. In this connection, the degree of increase of energy of
the electrons until they impinge upon the target is merely a
function of the value of the applied high voltage.
[0014] With the aforementioned embodiment, the anode is expediently
embodied in an essentially ring-shaped or annular configuration, so
that the electrons pass through the opening in the anode and in so
doing are accelerated. This enables in a particularly simple manner
for the electrons to be directed upon the target, which in the
direction of radiation of the electron beam is disposed downstream
of the anode.
[0015] In order to concentrate the energy of the electrically
charged particles upon a spatially limited portion of the target,
it is expedient to focus the electrically charged particles upon
the target.
[0016] Pursuant to a further development of the aforementioned
embodiment, the electrically charged particles are focused via at
least one electromagnetic optics mechanism. Such electromagnetic
optics can be realized in a straightforward and hence economical
manner, so that the inventive method is easy and hence economical
to carry out.
[0017] The target can be formed by any desired target that upon
irradiation with electrically charged particles emits UV radiation,
especially EUV radiation. The target is expediently provided with
liquid droplets, whereby pursuant to a further development of this
embodiment the liquid is xenon or water. With the aforementioned
embodiments, no contaminations (debris) occur, which could occur
with a target that is comprised of solid bodies.
[0018] Pursuant to a further development, the target is a cluster
target.
[0019] The plasma is expediently produced in a vacuum.
[0020] Pursuant to a further development of the inventive method,
laser pulses having a high repetition rate of at least
approximately 1000 Hz are used.
[0021] Pursuant to another further development, the target is a
highly repetitive target.
[0022] Further developments of the inventive device are provided in
the dependent claims 15 to 23.
[0023] The invention will be described in greater detail
subsequently with the aid of the accompanying drawing, which
represents one embodiment of an inventive device.
[0024] The single figure of the drawing shows an inventive device 2
for carrying out an inventive method for generating EUV radiation.
The device 2 is provided with a laser, which is not illustrated in
the drawing, and which produces laser pulses having a repetition
rate of at least approximately 1000 Hz, and directs them onto
photoelectric transducer means in the form of a photocathode 4.
Under the effect of the laser pulses, pulses of electrons are
released from the photocathode 4 and move, in the form of an
electron beam 6, to a ring-shaped or annular anode 8. To accelerate
the electrons, a high voltage is applied to the anode 8. In the
electrical field that is formed between the photocathode 4 and the
anode 8, the electrons are accelerated in conformity with the
applied high voltage, so that their energy is greatly increased.
With this embodiment, the high voltage is selected such that the
energy of the electron pulses, after the acceleration in the
electrical field, is greater by a factor of 10.sup.3 than the
energy of the laser pulses produced by the laser.
[0025] Provided in the direction of radiation of the electron beam
6, downstream from the anode 8, are means, which are not
illustrated in the drawing, for the focusing of the electron beam
6; such means can be formed, for example, by electro-magnetic
optics. The electromagnetic optics focus the electron beam 6 onto a
target, which in this embodiment is formed by a highly repetitive
micro-droplet target that is comprised of xenon droplets 10.
[0026] When the electrons impinge upon the xenon droplets 10, a
highly charged plasma is produced that produces the EUV radation in
a wavelength range of 11 to 14 nm.
[0027] Due to the acceleration of the electrons in the electrical
field, and the increase in their kinetic energy that is connected
therewith, a high power is available for the irradiation of the
xenon droplets 10 even if the laser, which irradiates the
photocathode 4, has a relatively low power. With regard to the
production of the electron beam for the irradiation of the xenon
droplets, the inventive device 2 has a high stability, is compact
in construction, and is simple and hence economical to
manufacture.
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